A. Field of the Invention
The present invention relates to a visual pressure indicator. The present invention further relates to an endotracheal cuff including an inflatable visual pressure indicator.
B. Description of the Related Art
There are many situations when it is important to determine the level of the fluid pressure in a device. The situations can vary from liquid or gas flowing in a conduit to the air pressure in a tire or inflated device, such as an air mattress. One particularly important device in which it is necessary to determine fluid pressure is in an endotracheal tube.
An endotracheal tube is a medical device used in emergency and other situations to prevent blockage of a patient""s airway and/or provide general anesthesia during a surgical procedure. Endotracheal tubes are used for allowing the passage of respiratory or anesthetic gases into the lungs, while preventing entry of secretions from the upper airway of a patient into the patient""s trachea and lungs. The endotracheal tube also provides a passageway for a suction catheter to be inserted into the trachea to remove accumulation of mucus from the lung passageway and thereby to prevent infections.
An endotracheal tube comprises a flexible tube, usually made from plastic such as polyvinyl chloride (xe2x80x9cPVCxe2x80x9d), having an inflatable cuff at one of its ends. The tube is inserted into the trachea so that the cuff is inserted below the vocal cords and above the bronchial tubes of the patient. The cuff, once inflated, seals the tube against the walls of the trachea.
The cuff is inflated by way of a cuff inflation tube which is formed within the wall of the tube which connects the cuff to an air source. A valve is fitted to the end of the cuff inflation tube to accommodate the air source, typically a syringe. The syringe is used to inflate the cuff with air via the cuff inflation tube.
In order to obtain the benefits of using an endotracheal tube, the cuff must be properly inflated. However, because the cuff is enclosed by the walls of the trachea, a visual indication of proper inflation is not possible. In addition, there is a tendency to overinflate the cuff, thereby causing damage to the walls of the trachea. Moreover, even if originally properly inflated, it has been found that anesthetic gas can permeate through the cuff and cause overinflation which can cause tracheal necrosis and/or stenosis. Therefore, there have been many efforts in the art to devise an indicator that detects proper inflation of the cuff.
For instance, a typical indicator used to indicate proper inflation of the cuff is a molded balloon. The balloon is attached to the end of the inflation channel that leads to the inflatable cuff. Inflation of the molded balloon directly correlates to the inflation of the cuff within the patient""s trachea. Therefore, the balloon is designed to detect and indicate any changes in cuff pressure by visual inspection, or by pressing the balloon to xe2x80x9cfeelxe2x80x9d the air pressure. However, the balloon is generally not sensitive enough to detect small pressure changes.
U.S. Pat. No. 4,361,107 to Gereg discloses a pressure indicating device for use with an endotracheal cuff. The device is added to a normal pilot balloon to indicate that a preset pressure has been exceeded. The device is folded inside itself when a low pressure is present, and becomes unfolded and elongated when a preset pressure has been exceeded. However, these indicators are often unreliable and prone to breakage.
U.S. Pat. No. 4,134,407 to Elam discloses a monitoring system for detecting the pressure and volume of an endotracheal cuff. The monitoring system is comprised of an elastomer balloon housed in a rigid cage having a plurality of windows which is designed to continuously indicate the state of collapse or expansion of the cuff of an endotracheal tube. The balloon monitor is connected in series with the pneumatic channel through which the cuff is inflated. The volume of the balloon may be observed visually with reference to its state of inflation, thereby visually indicating the level of inflation of the cuff. In addition, electrical means may be arranged between the balloon and the inner surface of the cage to produce a warning signal in the event of cuff overdistension and an alarm signal in the event of cuff collapse.
However, there are various disadvantages associated with this type of indicator. First, the visual indication of overinflation is detected by an inflation of a cavity of the balloon. There are various degrees to which the balloon may overinflate, and often times, it is left to the subjective determination of the health care professional to determine whether there is a potential overinflation. Therefore, this device lacks a simple, reliable, and objective indication for determining a dangerous overinflation of the cuff. While overinflation of the cuff may be determined by installing electrical means within the balloon, this is extremely costly.
U.S. Pat. No. 4,178,939 to Stephens discloses an apparatus for visually indicating the degree of inflation of an inflatable cuff which is adapted to be inserted into a body passageway. The apparatus comprises a hollow-walled tubular member formed with a plurality of ridges and valleys and is selectively inflatable into a balloon-like shape in response to the pressure of air applied to the cuff. The level of inflation of the cuff is subjectively determined by visual inspection of the inflatable balloon. Thus, this apparatus has similar disadvantages as it does not provide an objective and definitive determination of whether there is a dangerous overinflation of the cuff, but only indicates that an overinflated condition is present.
U.S. Pat. No. 4,856,510 to Kowaleski discloses a tracheal tube including an indicator assembly. The indicator assembly includes a pilot balloon and control balloon serially arranged to an inflation cuff, with the control balloon having a higher compliance than the pilot balloon and being connected directly to the inflation tube. The control balloon, because of its higher compliance, expands readily with very little increase in internal pressure. The result is that the pressure within the control balloon and the tracheal cuff remain fairly constant regardless of the amount of air introduced into the pilot balloon. However, the indicator assembly does improve the ease at which an overinflation may be detected. In addition, this indicator assembly is relatively complex in design, requiring multiple parts.
U.S. Pat. No. 4,617,015 to Foltz discloses a visual pressure indicator for endotracheal cuffs. The indicator comprises an indicating diaphragm which is sealingly positioned within a body by means of a cap. A hole is positioned within the cap to allow protrusion of an indicating stem of the diaphragm. The air space between the diaphragm and the body is connected in fluid communication with the cuff supply tube by means of passageways. The indicating diaphragm of the indicator flexes as the pressure within the cuff increases. As this pressure increases, the indicating stem of the diaphragm increasingly protrudes from the hole in the cap affixed to the body of the indicator. This indicating system has disadvantages, as there is no definitive and objective indication for determining when a dangerous overinflation has been reached. In addition, it is relatively complex in design, which is relatively expensive to manufacture.
Other types of indicator systems include the use of external pressure gauges, which measure the cuff pressure. An example of an external pressure gauge is manufactured by Rusch, Inc., in Duluth, Ga. However, these gauges are often extremely costly.
In one aspect, the present invention provides an indicator for visually indicating a pressure level of a fluid in a pressure source. The indicator comprises an inflatable body having a notched section with opposing edge portions that are separated by a gap when the inflatable body is in an uninflated condition. The inflatable body further includes a port for connecting the inflatable body to the pressure source whereby upon inflation of the inflatable body, there is relative movement of the opposing edge portions in a direction so as to decrease the size of the gap and thereby indicate that a predetermined pressure has been reached.
In a further aspect, the present invention provides a surgical tube with an inflatable cuff having a visual indicator. The inflatable cuff is disposed on the surgical tube and includes an inflation conduit leading from the cuff. The visual indicator is attached in series with the inflation conduit and includes an inflatable body having a notched section separated by a gap with opposing edge portions. The inflatable body further includes a port for connecting the inflatable body to the inflatable cuff whereby upon inflation of the inflatable body, there is relative movement of the opposing edge portions in a direction so as to decrease the size of the gap and thereby indicate that a predetermined pressure has been reached in the cuff.